A MEMS micro-mirror device is a device that contains a Micro-Electrical-Mechanical-System with a reflective surface. The optical MEMS may comprise a cylindrical, elliptical, rectangular or square micro-mirror that is adapted to move and to deflect light over time. The micro-mirror is connected by suspended arms to a fixed part and can tilt and oscillate along one or two axis. For example it can oscillate vertically and horizontally. Different actuation principles can be used, including electrostatic, thermal, electro-magnetic or piezoelectric. MEMS devices are known in which the area of these micro-mirrors are around a few mm2. In this case, the dimensions of the MEMS device, comprising the packaging, is approximately ten mm2. This device is usually made of silicon, and can be encapsulated in a package that can include the driving actuation electronics. Various optical components, such as for example lenses, beam combiner, quarter-wave plates, beam splitter and laser chips, are assembled with the packaged MEMS to build a complete system.
A typical application of the MEMS micro-mirror devices is for projection systems. In a projection system, a 2-D image or a video can be displayed on any type of surface. In a colour system, each pixel is generated by combining modulated red, green and blue laser light sources, by means of, for example, a beam combiner. A MEMS micro-mirror device directs the light of the laser light source to a projection surface and reproduces the image, or the video, pixel-by-pixel. By means of its oscillations, the micro-mirror within the device will continuously scan from left to right and from top to bottom, or according to a different trajectory including e.g., Lissajou trajectories, so that each pixel of the 2-D image is displayed on the screen.
Typically, the micro-mirror of a MEMS micro-mirror device is able to oscillate along one axis. Therefore, in order to display a 2-D image on a screen a projection system will require two MEMS micro-mirror devices; a first MEMS micro-mirror device is required to deflect light along the horizontal and a second MEMS micro-mirror device is required to deflect light along the vertical. During operation, the micro-mirror of the first MEMS micro-mirror device receives light from the beam combiner and deflects the light to the micro-mirror of the second MEMS micro-mirror device. The micro-mirror of the second MEMS micro-mirror device will in turn deflect the light to the display surface where it will appear as a pixel. The micro-mirror of the first MEMS micro-mirror device will oscillate to scan the light along the horizontal thereby displaying the first row of pixels on the display surface. The micro-mirror of the second MEMS micro-mirror device will oscillate about its oscillatory axis so that light received from the micro-mirror of the first MEMS micro-mirror device is scanned along the vertical. The combined effect of the oscillating micro-mirrors is that the light from the beam combiner is scanned in a zig-zag or raster pattern along the display surface. The process is continuous so that a complete image is visible to the viewer on the display surface. The first and the second MEMS micro-mirror devices are precisely positioned such that the oscillatory axes of the respective micro-mirrors are orthogonal; this ensure that all the light received by the micro-mirror of the first MEMS micro-mirror device will be deflected to the micro-mirror of the second MEMS micro-mirror device as the micro mirrors oscillate.
Other MEMS micro-mirror devices comprise a micro-mirror which can oscillate along two orthogonal axes. Such a micro-mirror can scan the light beam in two dimensions. Therefore, to display a 2-D image on a display surface a single mirror will oscillate about two axes to scan the light in a zig-zag, lissajou or raster pattern over the display surface. Various methods of oscillating the micro-mirrors are employed. For example, an electrostatic means; thermal means; electro-magnetic means, or piezoelectric means.
Projection systems in general are used to project images or videos onto a display surface. The projection systems currently used to project 3-D images on a display surface are complex and expensive. There is a need in the art for a simplified means and method which will enable the projection of a 3-D image.
It is an aim of the present invention to obviate or mitigate one or more of the aforementioned disadvantages.